拟康宁木霉活菌体处理含铜废水

以拟康宁木霉(Trichoderma koningiopsis)活菌体为吸附剂探讨了接触时间、初始铜浓度、投菌量、葡萄糖用量、碱浓度等因素对木霉活菌体处理含铜废水效果的影响.结果表明,在初始铜浓度100 mg/L,投菌量3 g/L,预处理碱浓度0.2 mol/L的条件下,木霉活菌体吸附铜效果最佳,吸附量可达5.01 mg/g(湿).吸附Cu前后的拟康宁木霉菌降解四环素实验结果表明,吸附前后木霉对有机物均有降解效果,吸附过程属活菌体吸附.TEM结果显示,木霉去除铜的机制为表面吸附/络合和胞内富集,FTIR揭示了羟基是活性菌体吸附的主要基团,XRD分析结果证实了羟基与铜结合并以水蓝铜矾[Cu4(SO4)(OH)6H2O]形式络合于菌种细胞壁上,Langmuir吸附等温线较好地拟合了活菌对铜离子的吸附,表明菌体对铜离子主要为均质单层吸附.     

Characterization of adsorbent composition in co-removal of hexavalent chromium with copper precipitation

Mechanisms of hexavalent chromium co-removal with copper precipitation by dosing Na2CO3 were studied with a series of well-designed batch tests using solutions containing 150 mg l-1 Cu(II) and 60 mg l-1 Cr(VI). It was found that direct precipitation of chromium through formation of copper-chromium bearing precipitates (in the form of CuCrO4) was one of the main mechanisms contributing to chromium co-removal at pH close to 5.0, and adsorption of chromium at a higher pH by freshly formed copper-carbonate precipitates (adsorbent) contributed to further chromium co-removal. Since, according to solubility products, neither copper-carbonate nor copper-hydroxide precipitates can be produced at pH around 5.0 for a pure 150 mg l-1 copper precipitation, characterization of copper-carbonate precipitates (adsorbent) was carried out through developing pC-pH curves of the systems by both equilibrium calculations and MINEQL+ 4.5 (a chemical equilibrium modeling software), and also through laboratory determination of the precipitate composition, such as gravimetric analyses, inorganic carbon percentage and EDAX spectrum analyses. CuCO3.Cu(OH)2, or a combination of CuCO3.Cu(OH)2 (in majority) and Cu(OH)2 (in minority) were suggested to be the major constituent of the precipitates obtained from the copper solution with Na2CO3 dosing.     

褐煤对废水中酸性红B的吸附去除

选用褐煤作为廉价吸附剂,脱除模拟废水中染料酸性红B。研究了褐煤对废水中酸性红B的吸附动力学、等温吸附模式,考察了pH、褐煤投加量以及离子强度(NaCl)对吸附效果的影响。结果表明,吸附动力学较好地符合准二级速率方程(R2=1.000),并且以化学吸附为主;吸附等温式满足Langmuir方程(R2=0.986),最大单分子层吸附量为42 mg/g;废水中染料的去除率随溶液pH的减小而明显增加,在pH=1时,去除效果最好,证实吸附过程存在静电吸引及化学键合;在一定条件下,溶液中酸性红B的去除率随褐煤投加量增加而增加;吸附效果随溶液中离子强度(NaCl)的增加而增强。说明褐煤可以作为一种廉价吸附材料,用于处理含染料废水。     

纳米铁酸铜催化过硫酸盐降解酸性红FRL

采用共沉淀法-焙烧制备纳米铁酸铜催化剂,利用扫描电镜(SEM)、X射线光电子能谱(XPS)和X射线衍射 (XRD)对催化剂进行表征。以酸性红FRL为降解目标物,研究此催化剂催化过硫酸钠降解酸性红FRL的性能。考察了氧化剂浓度、催化剂用量和初始染料浓度对降解的影响。结果表明:催化剂经700 ℃焙烧3 h,可得到完整晶相的CuFe2O4;当初始污染物浓度为20 mg/L,过硫酸盐浓度为2.0 g/L,催化剂用量为2.0 g/L时,降解2.5 h,酸性红FRL染料溶液的降解率可达85.3%。实验所得催化剂可重复使用5次,同时酸性红FRL降解过程遵循准一级动力学方程。     

Experimental design methodology for the preparation of carbonaceous sorbents from sewage sludge by chemical activation--application to air and water treatments

The objective of this study is to optimize experimental conditions of sorbent preparation from sewage sludge using experimental design methodology. Series of carbonaceous sorbents have been prepared by chemical activation with sulfuric acid. The sorbents produced were characterized, and their properties (surface chemistry, porous and adsorptive properties) were analyzed as a function of the experimental conditions (impregnation ratio, activation temperature and time). Carbonaceous sorbents developed from sludge allow copper ion, phenol and dyes (Acid Red 18 and Basic Violet 4) to be removed from aqueous solution as well as VOC from gas phase. Indeed, according to experimental conditions, copper adsorption capacity varies from 77 to 83 mg g(-1), phenol adsorption capacity varies between 41 and 53 mg g(-1) and VOC adsorption capacities (acetone and toluene) range from 12 to 54 mg g(-1). Each response has been described by a second-order model that was found to be appropriate to predict most of the responses in every experimental region. The most influential factors on each experimental design response have been identified. Regions in which optimum values of each factor were achieved for preparation of activated carbons suitable for use in wastewater and gas treatments have been determined using response surfaces methodology. In order to have a high mass yield and to minimize the energetic cost of the process, the following optimal conditions, 1.5 g of H2SO4 g(-1) of sludge, 700 degrees C and 145 min are more appropriate for use of activated carbon from sludge in water and gas treatments.     

Characterization of primary precipitate composition formed during co-removal of Cr(VI) with Cu(II) in synthetic wastewater

BACKGROUND, AIMS AND SCOPE: Hexavalent chromium [Cr(VI)] cannot react with either carbonate or hydroxide to form chromium precipitates. However, by using a precipitation technology to treat plating wastewater containing Cr(VI), Cu(II), Ni(II) and Zn(II), approximately 78% of Cr(VI) (initial 60 mg/L) was co-removed with the precipitation of Cu(II), Ni(II) and Zn(II) (each 150 mg/L) by dosing with Na2CO3 (Sun 2003). Direct precipitation by forming Cu(II)-Cr(VI) precipitates followed by adsorption of Cr(VI) onto freshly formed Cu-precipitates was subsequently found to be the main mechanism(s) involved in Cr(VI) co-removal with Cu(II) precipitation by dosing Na2CO3 stepwise to various pH values (Sun et al. 2003). This study was. carried out to further characterize the formation of primary precipitates during the early stages of copper precipitation and simultaneous removal of Cr(VI) with Cu(II). METHODS: Test metal-solutions were prepared with industrial grade chemicals: CuCl2 x 2H2O, Na2SO4 and K2Cr2207. NaCO3 was added drop-wise to synthetic metal-solution to progressively increase pH. For each pH increment, removal of soluble metals was detected by atomic absorption spectrophotometer (AAS) and surface morphology of precipitates was analyzed by scanning electron microscope (SEM). To further characterize the formation of primary precipitates, a series of MINEQL+ thermodynamic calculations/analyses and equilibrium calculations/ analyses were conducted. RESULTS AND DISCUSSION: MINEQL+ thermodynamic calculation indicated that, for a system containing 150 mg/L Cu(II) and 60 mg/L Cr(VI) with gradual Na2CO3 dosing, if any precipitates can be formed at pH 5.0 or lower, it should be in the form of CuCrO4. Comparison tests using systems containing the same equivalent of Cu(II) plus Cr(VI) and Cu(II) plus SO4(2-) showed that the precipitation occurred at a pH of around 5.0 in the Cu(II)-Cr(VI) system and around 6.0 in the Cu(II)-SO4(2-) system. The discrepancy of the precipitation was indeed caused by the formation of Cu-Cr precipitates. The initiation of copper removal at pH around 5.0 for the Cu-Cr co-removal test was not attributable to the formation of Cu-CO3 precipitates, instead, it was most likely through the formation of insoluble Cu-Cr precipitates, such as CuCrO4 and CuCrO4 x 2Cu(OH)2. Experimental tests, equilibrium calculations, MINEQL+ thermodynamic calculations and surface morphologies for systems using higher concentrations of Cu(II) and Cr(VI) further verified the most probable composition of primary precipitates is copper-chromate. CONCLUSION: In the Cu-Cr co-removal test with Na2O3 dosing to increase pH and induce metal precipitation, copper-chromate precipitates are the primary precipitates produced and contribute to the initial simultaneous removal of copper and chromium.     

多基团秸秆纤维对水体中铜/磺胺甲恶唑复合污染物的定量吸附性能

以秸秆纤维为研究对象,通过醚化和接枝化修饰方法赋予其纤维结构的季胺基(-N⁺)、羧基(-COOH)等,从而制备出多基团纤维材料(NCS)。在一元和二元吸附体系中,考察了NCS对不同pH水体中铜/磺胺甲恶唑(SMZ-Cu)复合污染物的去除效果。Langmuir吸附等温线拟合结果表明,NCS对SMZ和Cu(Ⅱ)的最大理论吸附量分别为59.76 mg·g⁻¹和4.71 mg·g⁻¹,以及对络合物中SMZ和Cu(Ⅱ)的最大理论吸附量分别为56.21 mg·g⁻¹和5.54 mg·g⁻¹。吸附过程也符合准二级动力学方程,属于化学吸附。相比而言,NCS在一元吸附体系中更倾向单一吸附SMZ而不是Cu(II)。而且,多重相互作用使NCS在二元吸附体系中主要吸附SMZ-Cu为主,而不是单一污染物。密度泛函理论(DFT)计算不但验证了上述结果,还定量地解释在单一吸附系统中,NCS的-N⁺结构中-COOH与SMZ中磺酰氨氮结合最稳定,而C-N则与Cu结合能最大;在二元吸附体系中,最主要的吸附结构是SMZ-Cu以Cu接近NCS方式,而络合-解络合-再络合模式是该体系中Cu被吸附增加的原因。     

建筑垃圾对雨水径流中Cu的吸附特性

以砖混建筑垃圾为研究对象,采用人工模拟雨水,通过静态和动态吸附实验研究了不同粒径粒级建筑垃圾对雨水径流中Cu的吸附效果。结果表明,准二级动力学模型比准一级动力学模型能更好地描述建筑垃圾对Cu的吸附过程;Freundlich等温模型能较好地拟合其等温吸附过程;不同粒径粒级建筑垃圾均对雨水径流中的Cu具有较好的净化效果,去除率均超过90%,粒径粒级越小,对Cu的净化效果越好,但其渗透性能越差;建筑垃圾的粒径粒级对Cu的吸附平衡时间、吸附速率和吸附量具有重要影响,粒径粒级2.36~4.75 mm的建筑垃圾对Cu的平衡吸附速率和平衡吸附量最大,分别为4.1 μg/min 和12.4 μg/g。     

Adsorption/desorption of copper by a sandy soil amended with various rates of manure, sewage sludge, and incinerated sewage sludge

Organic amendments are sometimes applied to agricultural soils to improve the physical, chemical, and microbiological properties of the soils. The organic fractions in these soil amendments also influence metal reaction, particularly the adsorption and desorption of metals, which, in turn, determine the bioavailability of the metals and hence their phytotoxicities. In this study, a Quincy fine sandy (mixed, mesic, Xeric Torripsamments) soil was treated with 0 to 160 g kg(-1) rates of either manure, sewage sludge (SS), or incinerated sewage sludge (ISS) and equilibrated in a greenhouse at near field capacity moisture content for 100 days. Following the incubation period, the soil was dried and adsorption of copper (Cu) was evaluated in a batch equilibration study at either 0, 100, 200, or 400 mg L(-1) Cu concentrations in a 0.01M CaCl2 solution. The desorption of adsorbed Cu was evaluated by three successive elutions in 0.01M CaCl2. Copper adsorption increased with an increase in manure rates. At the highest rate of manure addition (160 g kg(-1) soil), Cu adsorption was two-fold greater than that by the unamended soil at all rates of Cu additions. With increasing rates of Cu additions, the adsorption of Cu decreased from 99.4 to 77.6% of Cu applied to the 160 g kg(-1) manure amended soil. The desorption of Cu decreased with an increase in rate of manure amendment. Effects of sewage sludge amendments on Cu adsorption were somewhat similar to those as described for manure additions. Likewise, the desorption of Cu was the least at the high rate of SS addition (160 g kg(-1)), although at the lower rates there was not a clear indication of the rate effects. In contrast to the above two amendments, the ISS amendment had the least effect on Cu adsorption. At the highest rate of ISS amendment, the Cu adsorption was roughly 50% of that at the similar rate of either manure or SS amendments, across all Cu rates.     

In situ immobilization of Cu(II) in soils using a new class of iron phosphate nanoparticles

This study tested the feasibility of using a new class of iron phosphate (vivianite) nanoparticles synthesized using sodium carboxymethyl cellulose (NaCMC) as a stabilizer for in situ immobilization of Cu(II) in soils. Transmission electron microscopy measurements demonstrated that the particle size was about 8.4+/-2.9 nm. Batch tests showed that nano-sized vivianite particles can effectively reduce the leachability and in vitro bioaccessibility of Cu(II) in three representative soils (calcareous, neutral, and acidic) at the low doses of 0.61 and 3.01 mg PO(4) g(-1) soil. The Cu leachability was evaluated by the toxicity characteristic leaching procedure and in vitro bioaccessibility was evaluated by the physiological based extraction test. In the case of soil amendment with nanoparticles in 3.01 mg PO(4) g(-1) soil, Cu leachability reduced 63-87% and Cu concentrations in TCLP extract decreased from 1.74-13.33 mg l(-1) to 0.23-2.55 mg l(-1) after those soils were amended for 56 d. Meanwhile, the bioaccessibility of Cu was reduced by 54-69%. Sequential extraction procedures showed the significant decrease of water soluble/exchangeable Cu(II) and carbonate bound fractions and concomitant increase of Cu residual fraction after the soils were amended with the nanoparticles, suggesting that the formation of copper phosphate minerals through precipitation and adsorption was probably responsible for the decrease of Cu availability in soils. Visual MINTEQ modeling further revealed that Cu(3)(PO(4))(2) and Cu(5)(PO(4))(3)OH were formed in the vivianite-solid Cu(II) system, resulting in the decreased solubility of the Cu(II) in the acidic pH range.     

赤泥质陶粒吸附模拟酸性废水中铜离子的行为

矿山酸性废水中重金属污染较普遍,利用赤泥陶粒对模拟酸性废水中的Cu2+进行净化处理。实验结果表明,当pH值为3、温度为30 ℃、Cu2+初始浓度为150 mg/L、陶粒添加量为20 g/L、吸附时间为4 h时,Cu2+的去除率达到95.06%。陶粒对Cu2+的吸附符合准二级动力学模型,相关系数为0.998 3,饱和吸附量为7.412 9 mg/g;等温吸附模型中更符合Langmuir等温吸附模型,相关系数为0.993 3。处理废水后的陶粒用硫酸-硝酸浸提,浸出液中重金属离子浓度均低于国家浸出毒性标准,表明陶粒是一种很好的酸性废水处理剂。吸附饱和的陶粒用1 mol/L的NaOH溶液再生效果好。实验结果表明,陶粒对Cu2+的吸附过程是物理吸附和化学吸附的共同作用。     

4A沸石对复合污染水体中Pb2+、Cu2+和Cd2+的去除

采用静态吸附法以4A沸石为吸附剂研究其对复合污染水体中Pb2+、Cu2+和Cd2+的竞争吸附特性,并探讨了影响吸附的环境因素。实验表明,在室温条件下,溶液pH5～6,4A沸石15 mg对10 mL复合污染溶液(Pb2+、Cu2+和Cd2+浓度分别为100 mg/L)吸附20 min时,对溶液中3种重金属的吸附去除率均可达99.8%以上。反应过程中4A沸石对3种重金属的吸附速率大小为Pb2+>Cu2+>Cd2+。复合污染水体中4A沸石对Pb2+、Cu2+和Cd2+的吸附符合Langmuir和Fre-undlich等温吸附方程,相关系数分别为0.9981、0.9901、0.9916和0.9638、0.9194、0.9689。经计算,4A沸石对Pb2+、Cu2+和Cd2+的饱和吸附量分别为129.9 mg/g、107.5 mg/g和99.0 mg/g。4A沸石吸附重金属离子达到吸附平衡的时间较短,对溶液pH值的适应性较好。吸附后的4A沸石可以再生利用,对铅离子洗脱重复利用性较铜离子和镉离子强。     

SA@L-Cys@Fe3O4磁性复合材料对含Cu(Ⅱ)废水的处理效能及其机理

以海藻酸钠(SA)、L-半胱氨酸(L-Cys)、CaCl₂和Fe₃O₄为原材料制备了一种环保型的磁性复合材料MSAL,以模拟废水和实际含铜电镀废水为研究对象,探索了pH、共存离子和吸附时间对Cu(II)吸附性能的影响。采用SEM-EDS、PPMS和XPS等分析手段对MSAL进行了表征,且探索了其可能的吸附机理。单因素条件优化实验结果表明：MSAL的适宜制备条件为30.0 g·L⁻¹ SA、6.0 g·L⁻¹ L-Cys、2.5 g·L⁻¹ CaCl₂、2.0 g·L⁻¹ Fe₃O₄;MSAL对Cu(Ⅱ)的吸附性能随pH增大而明显提高,并在pH为3.0~5.0时,对Cu(Ⅱ)维持较高的去除率;在pH=5时,MSAL对电镀废水中铜去除率可高达94.02%。吸附倾向于遵循拟准二级动力学模型和Langmuir等温模型,这表明吸附以单分子层吸附为主,并受化学过程控制,最大吸附容量可达到175.45 mg·g⁻¹。表征结果发现：MSAL具备出色的磁响应性,容易从溶液中被去除;吸附过程主要受离子交换作用以及氨基,羧基与Cu(Ⅱ)之间的配位作用影响。以上结果可为磁性复合材料在电镀废水中重金属污染治理奠定坚实基础。     

Biomass-derived materials in the remediation of heavy-metal contaminated water: removal of Cadmium(II) and copper(II) from aqueous solutions

Manganese-coated activated carbon (MCAC) and activated carbon were used in batch experiments for the removal of cadmium(II) and copper(II). Results showed that uptake of Cd(II) and Cu(II) was unaffected by increases in pH (3.0 to 8.5) or concentration (1 to 20 mg/L). Increased ionic strength (from 0.001 to 1 M NaNO3), however, significantly affected the uptake of Cd(II); adsorption of Cu(II) was not affected. Freundlich adsorption isotherm results indicated that MCAC possessed higher sorption capacity than activated carbon. Second-order rate constants were found to be 0.0386 for activated carbon and 0.0633 g/mg x min for MCAC for Cd(II) and 0.0774 for AC and 0.1223 g/mg x min for MCAC for Cu(II). Column experiments showed that maximum sorption capacity of MCAC was 39.48 mg/g for Cu(II) and 12.21 mg/g for Cd(II).     

氧化石墨烯修饰MoS2-PAN吸附膜对铜离子吸附性能的影响

通过氧化石墨烯(GO)对硫化钼(MoS₂)-聚丙烯腈(PAN)进行改性处理,采用相转化法成功制备了对水溶液中Cu²⁺进行吸附的GO-MoS₂-PAN改性吸附膜。通过扫描电镜(SEM)、傅里叶变换红外光谱(FTIR)及接触角测试对该吸附剂材料进行了表征。探究了不同GO固含量对GO-MoS₂-PAN改性吸附膜的孔隙率、纯水通量以及接触角的影响。在pH为5、Cu²⁺质量浓度为100 mg·L^-1的溶液中,GO固含量为0.03%的改性吸附膜对Cu²⁺的最大平衡吸附量达到224.28 mg·g^-1,且其脱附率为84%。结果表明,改性吸附膜对溶液中Cu²⁺的吸附动力学符合准二级动力学模型,等温吸附过程符合Freundlich等温吸附模型,热力学分析结果表明该吸附过程为自发吸热过程。     

Effect of fly ash characteristics on the removal of Cu(II) from aqueous solution

Fly ash is a particulate substance containing metal oxides, carbon and other microelements. In this study, fly ashes with different quantities of carbon and minerals prepared by a thermal process in the laboratory were used as adsorbents to investigate the contribution of precipitation and adsorption to the removal of aqueous Cu(II). Experimental results showed that the specific surface area of fly ash increased linearly with the quantity of carbon. The specific surface areas of the carbon and mineral fraction were 60 m2/g and 0.68 m2/g, respectively. The specific adsorption capacities of carbon ranged from 2.2 to 2.8 mg Cu/g carbon, while those for mineral were only about 0.63 to approximately 0.81 mg Cu/g mineral. Consequently, the carbon fraction in fly ash was important in the removal of Cu(II) at pH 5. However, Cu(II) removal owing to precipitation increases with a decreasing carbon fraction and the contribution of copper precipitation was estimated to be approximately 23% to approximately 82% of total removal, depending on the carbon fraction of fly ash.     

Metal bioaccumulation and metallothionein concentrations in larvae of Crassostrea gigas

Larval stages of bivalve molluscs are highly sensitive to pollutants. Oysters from a hatchery from Normandy (English Channel) were induced to spawn, and fertilized eggs were exposed to copper or cadmium for 24 h. Metal accumulation (from 0.125 to 5 microg Cu L(-1) and from 25 to 200 microg Cd L(-1)) and MT concentrations were measured in larvae. Compared to controls, larvae accumulated copper and cadmium with an increase in MT concentrations particularly with cadmium (i.e. 130.96 ng Cu (mg protein)(-1) and 12.69 microg MT (mg protein)(-1) at 1 microg Cu L(-1) versus 23.19 ng Cu (mg protein)(-1) and 8.92 microg MT (mg protein)(-1) in control larvae; 334.3 ng Cd (mg protein)(-1) and 11.70 microg MT (mg protein)(-1) at 200 microg Cd L(-1) versus 0.87 ng Cd (mg protein)(-1) and 4.60 microg MT (mg protein)(-1) in control larvae). Larvae were also obtained from oysters of a clean area (Arcachon Bay) and a polluted zone (Bidassoa estuary) and exposed to copper in the laboratory, their MT concentration was measured as well as biomarkers of oxidative stress. Biomarker responses and sensitivity to copper for the larvae from Arcachon oysters were higher than for those from Bidassoa.     

β-环糊精接枝羧甲基壳聚糖吸附剂的制备及其性能

采用γ-氨丙基三乙氧基硅烷化学修饰活化后的硅胶,以戊二醛为交联剂,接上羧甲基壳聚糖,继而接枝上β-环糊精作为功能单体,制备了一种用于分离富集水样中Cu(Ⅱ)的固相萃取新材料。利用红外光谱(FT-IR)、比表面分析(BET)、X射线衍射光谱(XRD)以及热重分析(TG)等方法对吸附剂进行结构表征。采用火焰原子吸收(FAAS)作为检测手段,考察了溶液pH、振荡时间、吸附剂用量、样品流速、洗脱液浓度和体积等对吸附剂吸附Cu(Ⅱ)的影响。吸附剂饱和吸附容量为9.37 mg/g,最大富集倍数高达350。吸附过程能用准二级动力学模型和Langmuir等温吸附方程进行很好的拟合。应用于环境水样中Cu(Ⅱ)的分离富集与测定,回收率在96.8%~105.2%之间,效果较好。     

Impacts of pH and ammonia on the leaching of Cu(II) and Cd(II) from coal fly ash

Many coal-fired power plants are implementing ammonia-based technologies to reduce NO(x) emissions. Excess ammonia in the flue gas often deposits on the coal fly ash. Ammonia can form complexes with many heavy metals and change the leaching characteristics of these metals. This research tends to develop a fundamental understanding of the ammonia impact on the leaching of some heavy metals, exemplified by Cu(II) and Cd(II), under different pH conditions. Batch results indicated that the adsorption is the main mechanism controlling Cu(II) and Cd(II) leaching, and high concentrations of ammonia (>5,000 mg/l) can increase the release of Cu(II) and Cd(II) in the alkaline pH range. Based on the chemical reactions among fly ash, ammonia, and heavy metal ion, a mathematical model was developed to quantify effects of pH and ammonia on metal adsorption. The adsorption constants (logK) of Cu(2+), Cu(OH)(+), Cu(OH)(2), and Cu(NH(3))(m)(2+) for the fly ash under investigation were respectively 6.0, 7.7, 9.6, and 2.9. For Cd(II), these constants were respectively 4.3, 6.9, 8.8, and 2.6. Metal speciation calculations indicated that the formation of less adsorbable metal-ammonia complexes decreased metal adsorption, therefore enhanced metal leaching.     

Thermodynamics of metal cation binding by a solid soil-derived humic acid: binding of Fe(III), Pb(II), and Cu(II)

Metal binding and release by solid humic acids (HAs) in soils and sediments can affect metal mobility and bioavailability. Isotherms for tight binding of Fe(III), Pb(II) and Cu(II) by a solid humic acid at pH2.0 fit the Langmuir binding model. Low pH was chosen to protonate the HA carboxylate groups and avoid metal cation hydrolysis. Binding of Fe(III), Pb(II) and Cu(II) occurs in one detectable step labeled A. Site capacities nu(A) are temperature-independent from 10.0 to 40.0 degrees C and point to binding by charge-neutralization to form solid complexes M(OOC-R)(n)(s), where n appears to be 2 for Pb(II) and 3 for Fe(III). Thermodynamic data pairs (DeltaH(A), DeltaS(A)) for metal binding are linearly correlated with previous data for Ca(II), Co(II) and Mg(II) binding by solid HAs.